Visitors to dozens of Web sites purportedly linked to illegal file sharing and counterfeit goods were greeted by this message.

The U.S. government has launched a major crackdown on online copyright infringement, seizing dozens of sites linked to illegal file sharing and counterfeit goods.

Torrent sites that link to illegal copies of music and movie files and sites that sell counterfeit goods were seized this week by the Immigration and Customs Enforcement division of the Department of Homeland Security. Visitors to such sites as Torrent-finder.com, 2009jerseys.com, and Dvdcollects.com found that their usual sites had been replaced by a message that said, "This domain name has been seized by ICE--Homeland Security Investigations, pursuant to a seizure warrant issued by a United States District Court."

"My domain has been seized without any previous complaint or notice from any court!" the owner of Torrent-Finder told TorrentFreak, which listed more than 70 domains that were apparently part of the massive seizure.

DHS representatives did not immediately respond to a request for comment.

The seizures came after a Senate committee unanimously approved a controversial proposal earlier this month that would allow the government to pull the plug on Web sites accused of aiding piracy. The Combating Online Infringement and Counterfeits Act (COICA) allows a Web site's domain to be seized if it "has no demonstrable, commercially significant purpose or use other than" offering or providing access to unauthorized copies of copyrighted works.

The proposal has garnered support from dozens of the largest content companies, including video game maker Activision, media firms NBC Universal and Viacom, and the Motion Picture Association of America and Recording Industry Association of America lobbying groups. However, critics such as engineers and civil liberties groups say the COICA could balkanize the Internet, jeopardize free speech rights, and endanger legitimate Web sites.

The battle against online file sharing has ramped up. Earlier today, a Swedish court upheld the copyright conviction of the founders of The Pirate Bay, a notorious file-sharing site. In October, a U.S. district judge issued an injunction against Lime Wire, the company that operated the popular file-sharing software LimeWire. In May, a judge granted summary judgment in favor of the music industry's claims that Lime Group, parent of LimeWire software maker Lime Wire, committed copyright infringement, engaged in unfair competition, and induced copyright infringement.